In order to achieve high energetic efficiency and cooling, household and commercial cooling systems use nowadays variable capacity compressors (VCC). Such compressors have, as a characteristic, adjustments in the cooling capacity by varying the cooling-gas pumping velocity, that is, the velocity of the mass flow thereof according to the need of the system and its demand for cooling.
The variation of the mass flow takes place from a minimum value to a maximum value, this value range being proportional to the rotation of the electric motor that drives the airtight variable capacity compressor. Rotation variation is achieved on these compressors by means of an electric control called frequency inverter, which adjusts the voltage and frequency applied to the electric motor.
In general, the frequency inverter is provided with a number of electronic circuits with different functions, as for example, a power circuit with input stage for filtering electromagnetic interference and a “rectifying bridge” stage for converting an alternating voltage from an external feed source to a direct voltage, a control circuit (Digital Signal Processor—DSP), an auxiliary feed source for generating the internal voltages for other circuits of components of the inverter, a circuit formed by power semiconductors to actuate the electric motor employed on the compressor, among others.
One observes that the electric connection and fixation of the frequency inverter to the airtight compressor requires one to carry out a number of steps in the production line. This results in loss of efficiency and high cost in the production and mounting of the frequency inverter.
Another problem observed refers to the use of cables for electric connection between the frequency inverter and the connector, which generally is provided with three pins, of the airtight compressor. The use of a cable requires fixation thereof to the printed-circuit board of the frequency inverter, which results in an increase in the general production costs and time, due to the need to weld the cable to the inverter board or to the use of an additional connector on the board.
Additionally, one observes in the prior art that the frequency inverter is arranged in a closed plastic housing, which fits onto a fence of the airtight compressor, being attached by means of screws in order to meet the regulation requirements.
The above problems are observed upon carrying out the steps of fixing the frequency inverter to the fence of the airtight compressor, which will be detailed hereinafter.
The first step is carried out by fixing the components and circuits that compose the frequency invertor to the printed-circuit board.
After this step, the connector for feeding the motor of the airtight compressor is mounted onto the printed-circuit board. The grounding connector of the electromagnetic interference filtering (ground connection point) is mounted to the printed-circuit board.
The grounding derivation terminal is pressed onto the plastic body of the outer housing.
The printed-circuit board is then mounted onto the plastic base of the plastic body of the outer housing.
A motor connection cable is attached to the connector for feeding the airtight compressor motor previously mounted to the printed-circuit board. A grounding cable of the electromagnetic interference filtering circuit is connected to the connector located on the printed-circuit board.
The cable from the grounding connector of the electromagnetic interference filtering circuit is connected to the grounding terminal attached to the plastic body.
The plastic body of the outer housing is mounted onto the plastic base, so that the previously mounted cables pass through orifices existing in said body.
The plastic cover is then closed, making interface with the plastic base and body, the cover is screwed to the base-and-body assembly, the motor cable connector is coupled to the connector of the airtight compressor, a derivation of the grounding cable of the electromagnetic interference filtering circuit is coupled to the ground terminal of the compressor, the plastic assembly is fitted to the compressor through the orifice existing in the plastic body and the assembly is fixed to the airtight compressor by means of screws.